Answer this question truthfully
### Question: What causes Baker's cyst?
### Response: A Baker's cyst is caused by swelling in the knee. The swelling is due to an increase in synovial fluid - the fluid that lubricates the knee joint. When pressure builds up, fluid bulges into the back of the knee.
Baker's cyst commonly occurs with:
A tear in the meniscal cartilage of the knee Knee arthritis (in older adults) Rheumatoid arthritis Other knee problems